Lead
Saturn's Metal
Philalethes's 1668 Metamorphosis of Metals calls extracting the metallic seed from lead wasted labour: he says to obtain it from gold instead.
Eirenaeus Philalethes, Metamorphosis of Metals, chapter IV, 'Of the Seed of Gold; and whether other Metals have Seed'; 1668 publication confirmed by Indiana University's Keynes MS. 25 edition.
The alchemical sign for lead, also used for Saturn.
More context
Lead shares Saturn's planetary sign in alchemical notation. In Metamorphosis of Metals, published in 1668, Philalethes treats lead as imperfect gold, differing in digestion rather than basic substance. He reports miners' claims that lead becomes silver underground and argues that art can accelerate nature. Yet he recommends obtaining the metallic seed from mature gold, calling extraction from lead or tin wasted labour. His account makes lead a possible subject of transformation, without making it the obligatory starting material for every alchemical operation.
Light
For Philalethes, lead is potentially gold: its imperfection lies in incomplete maturation rather than a different metallic substance.
Shadow
Philalethes warns that obtaining the metallic seed from lead wastes labour when gold supplies it more readily.